Steerable beam antennas that allow for the transmission and/or reception of a highly directional electromagnetic signals are well-known in the art, as exemplified by U.S. Pat. No. 6,750,827; U.S. Pat. No. 6,211,836; U.S. Pat. No. 5,815,124; and U.S. Pat. No. 5,959,589. These exemplary prior art antennas include a waveguide feed that provides the evanescent coupling of electromagnetic waves between a waveguide feed including an elongate (typically rod-like) dielectric element, and a cylinder or drum spinning or rotating on an axis parallel to the axis of the dielectric element, and then radiating the coupled electromagnetic energy in directions determined by a diffraction grating provided by surface features (such as, for example, grooves) of the drum. By defining rows of features, wherein the features of each row have a different period, and by rotating the drum around an axis that is parallel to that of the dielectric element, the radiation can be directed in a plane over an angular range determined by the different periods.
As noted above, the typical waveguide feed used with a spinning drum antenna includes an elongate dielectric rod, typically of quartz. Such rods are inherently fragile, and their placement usually requires some manual labor to obtain the needed precision. Furthermore, the spinning drum with a groove pattern creates air flows for which the dielectric rod presents a bluff body that creates air vortices, thereby causing rod vibrations, and otherwise degrading dynamic antenna parameters.
Accordingly, it would be advantageous to provide a steerable beam antenna in which the problems associated with a rod-like dielectric coupling element are minimized or substantially reduced.